The present application relates to detector elements of a radiographic detector array. It finds particular application with flat panel, direct conversion detector arrays, but may also relate to other types of detector arrays where two or more detector elements are arranged to form a detector array. Such detector arrays are commonly used in medical, security, and/or industrial radiographic imaging systems, for example.
Radiographic imaging systems, such as projection radiography systems, computed tomography (CT) systems, line scanners, etc., provide information, or images, of the inside of an object under examination (e.g., interior aspects of an object under examination). That is, an object under examination by the radiographic imaging system is exposed to radiation, and one or more images are formed based upon the radiation absorbed by the object, or rather an amount of radiation that is able to pass through the object. Typically, highly dense objects absorb (e.g., attenuate) more radiation than less dense objects, and thus an object having a higher density, such as a bone or metal object, for example, will appear differently than less dense objects, such as fatty tissue or clothing, for example.
Traditionally x-rays images were formed using x-ray film. The film was exposed to radiation, or light yielded from the radiation (e.g., if intensifying screens were placed between the film and the radiation source), and a visible pattern of metallic black silver was produced on the film. The degree of blackening (e.g., the amount of metallic black silver produced) depended upon the intensity of the radiation (e.g., the magnitude of radiation absorbed by the object). Thus, the detector array was essentially comprised of an x-ray film and possibly one or more intensifying screens.
More recently, the x-ray film and the intensifying screens have been replaced with digital detector arrays, such as flat panel detector arrays, that are configured to convert radiation, either directly or indirectly, into electrical current that is measured to yield electrical signals. The amount of electric current measured is proportional to the number of photons that impact the digital detector array, and can be used to create an image(s) of the object under examination.
It will be appreciated to those skilled in the art that there are two basic types of digital detector arrays, direct conversion detector arrays and indirect conversion detector arrays. Direct conversion detector arrays are typically configured to convert detected radiation directly into electric charge using a crystalline or amorphous material, for example. Indirect conversion detector arrays are generally configured to convert detected radiation into another medium, typically light, before the electric charge is produced. Thus, for example, indirect conversion detector arrays may convert radiation into light using a scintillator material (e.g., Cadmium Tungstate, Bismuth Germanate, Cesium Iodide, Sodium Iodide, Lutetium Orthosilicate, an amorphous material, etc.) and may subsequently convert the light into electric charge using a photodetector array (e.g., a plurality of photodiodes). Generally, in both direct and indirect conversion detector arrays, the electric charge is detected/measured using a thin-film transistor (TFT) array comprising a two-dimensional (2D) capacitor array, but it may be detected/measured by other means known to those skilled in the art.
Regardless of the type of digital detector array, in some radiographic image applications it is preferable to manufacture the detector array using a plurality of detector elements (e.g., which are essentially identical in shape and size). In this way, if a portion of the detector array malfunctions, the malfunctioning portion of the detector array can be replaced without having to replace the entire detector array. Moreover the size of a detector array, if manufactured as one unit, may be limited due to manufacturing constraints. However, by fitting together a plurality of detector elements to form the completed detector array, the theoretical size of a detector array is virtually limitless. Thus, for a plurality of reasons, digital detector arrays are, at times, manufactured using a plurality of detector elements that are physically coupled together to form the completed detector array.
While manufacturing digital detector arrays from a plurality of detector elements has proven useful, there are several disadvantages to such a technique. For example, between respective detector elements there is a gap, which can allow radiation to pass through the detector array unimpeded and to interfere with electronics situated below the detector array. While this gap can be filled using a filler material, such as lead or loaded oxides, for example, that mitigates the amount of radiation that is capable of being passed through to the electronics, the detector pitch generally needs to be increased to accommodate the filler material. It can be appreciated, however, that a larger gap is undesirable because it puts a limit on how small the pixel pitch can be made.